The present invention is directed to a network interface for providing complete reception of data by a disconnected party when a disconnecting party requests termination of the communication.
A conventional Global System for Mobile Communication (GSM) network is described in "The GSM System for Mobile Communications," M. Mouly and M. Pautet, 1992, which is incorporated herein by reference. Briefly, the GSM network operates under GSM data services and supports the connection of GSM data services to data services of other networks, for example Public Switched Telephone Networks (PSTNs) and Integrated Services Digital Networks (ISDNs). The GSM standards call for an InterWorking Function (IWF). The IWF provides Mobile Switching Centers (MSCs) of the GSM network with protocol translation capabilities to interconnect GSM data services to data services of other networks. This protocol translation permits a data terminal connected to the GSM network to communicate with a data terminal connected to a PSTN or an ISDN, for example.
The data terminal, or terminal equipment, on the PSTN/ISDN side connects to the PSTN/ISDN via a modem or a terminal adaptor. The data terminal on the GSM network side, on the other hand, connects to the GSM network via a terminal adaptation function (TAF), a mobile station (MS), a radio channel between the MS and a base station system (BSS), and an "A-interface" between the BSS and an MSC. The MSC connects to the PSTN/ISDN, and has access to an internal or external IWF.
When establishing a data connection between the data terminals, data received from the PSTN/ISDN by the MSC goes to the IWF. The IWF converts data from the PSTN/ISDN to a form compatible with the A-interface, and sends the converted data back to the MSC for routing over the A-interface to the data terminal on the GSM side. The IWF also converts data received on the A-interface to a format compatible with the PSTN/ISDN data service for transmission to the PSTN/ISDN.
The IWF includes a memory for buffering the data arriving from the PSTN/ISDN to perform format conversion. This can lead to problems, however, when the PSTN/ISDN side initiates dropping the data connection (i.e., disconnection). The MSC normally responds to notification from the PSTN/ISDN that the connection has been dropped by immediately dropping the A-interface connection. This response, although appropriate for voice calls, can interrupt the A-interface while data destined for the data terminal on the GSM network side is still in the IWF memory. When this happens, some of the data destined for the data terminal on the GSM network side is lost.
A similar problem results when the data terminal on the GSM network side initiates dropping of the connection and there is data buffered in the IWF destined for the data terminal in the PSTN/ISDN network.